Vehicle seat

ABSTRACT

Provided is a vehicle seat having a high absorbing efficiency of impact energy upon rear end collision. The vehicle seat includes a pair of side frames that are arranged on the side, and lower frames and that connect lower portions of the pair of side frames to each other, in which a narrow portion including: a horizontal portion formed inside the pair of side frames along a longitudinal direction with a flexibility against a load equal to or more than a predetermined impact load, and an inclined portion extending from the horizontal portion via a bent portion inside the pair of side frames is formed on the lower frames.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 13/991,572, filed Jun. 4, 2013, which is a National Stage Entryapplication of PCT Application No. PCT/JP2011/078478, filed Dec. 8,2011, which claims the priority benefit of Japanese Patent ApplicationNo. 2010-273867, filed Dec. 8, 2010, the contents of all beingincorporated herein by reference.

BACKGROUND

Disclosed herein is a vehicle seat, and more particularly a vehicle seatwith an improved impact energy absorption efficiency upon rear endcollision.

An occupant on a seat is rapidly moved rearward, and the upper body ofthe occupant inclines rearward during a so-called rear end collisionwhere a rear portion of a vehicle such as a motor vehicle is in acollision from behind, or collides hard during a rearward travel.

Therefore, the upper body of the occupant rapidly approaches a seatbackof a vehicle seat due to the inertial force, and an impact is applied tothe body of the occupant. The seatback is mainly constructed by placinga cushion material on a metal seatback frame and covering the cushionmaterial with a skin material, which does not provide sufficientdeformation amount for the rapid rearward movement of the occupant uponrear end collision or the like and may not efficiently reduce a loadapplied to the body of the occupant. Moreover, the large load is appliedto the seatback and thus some damage may be caused to the seatback.

In order to solve the problems, Japanese Patent Document No. 4200580(“the '580 document”) proposes a technique configuring side frames(described as side members in this document) to bend when a rearwardload is applied to an upper portion of a seatback frame, therebymitigating the load applied to an occupant during the rearward movement.

Moreover, Japanese Patent Document Nos. 2000-118279 A (“the '279document”) and 2006-213201 A (“the '201 document”) propose a seatbackframe configured to have concavo-convex portions extending in a seatwidth direction, formed on a lower frame (cross frame in the '279document) and lower frame portion in the '201 document) constructed inthe seat width direction (right and left direction) below a seatbackframe. With the recesses and protrusion provided to extend in the seatwidth direction on the lower frame, when a large load is appliedrearward to the seatback frame, the concavo-convex portions can deform,thereby absorbing impact energy.

When a load is applied rearward as a result of a rearward movement ofthe occupant upon rear end collision or the like, the side frames bend,and the impact energy of the rearward movement is absorbed by theseatback frame disclosed in the '580 document. However, a position to bedeformed (bent portion) cannot be limited for deformation in theseatback in this document, and bends occur at any points in the up anddown direction on the side frames. As a result, the bending point cannotbe limited, and the impact energy is thus transmitted to the entireseatback frame, resulting in a decreased absorption efficiency of theimpact energy.

When a large load is applied rearward to the seatback frames disclosedin the '279 and '201 documents, the concavo-convex portions provided inthe seat width direction on the lower frame are deformed, therebyabsorbing the impact energy while the deformed position of the seatbackframe is limited to the portion below the seatback frame.

As described above, according to the techniques of the '279 and '201documents, the portion that tends to be bent by the large rearward loadis provided at a specific position, thereby deforming the portion thattends to be bent, and mitigating the impact upon rear end collision.However, a technique for increasing rigidity of portions other than theportion that tends to bend (deformation portion) to facilitate therestriction of the bent portion, thereby further restricting the bentposition, and efficiently absorbing the impact energy is needed.

Moreover, a technique of sufficiently sinking the body of the occupantinto the pressure receiving member provided for the seatback frame,thereby efficiently absorbing the impact energy, is needed. In otherwords, not a technique for facilitating deformation when a largerearward load is applied, but a technique for providing a properrigidity against the load and sufficiently sinking the body of theoccupant into the seatback frame, thereby efficiently absorbing theimpact energy, is needed.

SUMMARY

An object according to various embodiments of the present invention isto provide a vehicle seat capable of providing an improved rigidity ofportions other than portions which deform to absorb impact energy uponrear end collision, thereby efficiently absorbing the impact energy.Moreover, another object is to provide a vehicle seat with an improvedrigidity of portions other than portions that tend to bend (deformationportion) to facilitate restriction of the deformation portions, therebyfacilitating guidance of the seatback frame deformation. Further, stillanother object is to provide a vehicle seat capable of sufficientlysinking the body of an occupant, thereby efficiently absorbing theimpact energy.

The problems are solved by a vehicle seat according to variousembodiments of the present invention including a pair of side framesthat are arranged on the side, and lower frames that connect lowerportions of the pair of side frames to each other; in which a narrowportion including: a horizontal portion formed inside the pair of sideframes along a longitudinal direction with a flexibility against a loadequal to or more than a predetermined impact load, and an inclinedportion extending from the horizontal portion via a bent portion insidethe pair of side frames is formed on the lower frame.

As described above, the vehicle seat includes the narrow portions on thelower frame. Then, the narrow portion includes the horizontal portionprovided to extend approximately horizontally in the longitudinaldirection of the lower frame, namely in the right and left direction ofthe seat, and the inclined portion extending while bending from thehorizontal portion. The horizontal portion formed inside the side framesis configured to have the flexibility, and, when a predetermined impactload is applied to the vehicle seat upon rear end collision or the like,can deform to absorb the impact energy.

The impact load applied to the seatback frame constructing the vehicleseat upon rear end collision is a load applied mainly rearward, in moredetail, in a direction that the seatback frame inclines rearward. Thus,when the rearward impact load is applied to the seatback frame by therear end collision or the like, the horizontal portions having thenarrow portions can deform (bend), and the entire seatback frame thusdeforms to incline rearward, thereby absorbing the impact energy.

Then, the inclined portions bent and extended from the horizontalportions are provided to extend in directions other than the horizontaldirection. Thus, when the rearward inclination load is applied to theseatback frame upon rear end collision or the like, the horizontalportions deform to absorb the impact energy, while the inclined portionsare hard to deform, thereby increasing rigidity of portions other thanportions where the horizontal portions are provided. As a result, onlythe horizontal portions are caused to efficiently absorb the impactenergy.

Further, if the horizontal portions are provided, a lateral load (loadin a direction parallel to the extending direction of the horizontalportions) can be received at ridge portions of the horizontal portions,and the rigidity of the lower frame against the lateral load can thus beincreased. Further, the inclined portions can also receive the lateralload, and the rigidity against the lateral load is further increased.

In an embodiment, preferably, the lower frame includes a pair of lowerframe side portions arranged below the pair of side frames, and a lowerframe center portion that connects the pair of lower frame side portionsto each other; the lower frame side portion includes a side plate joinedto a side plate of the side frame, and an intermediate plate formed bybeing bent from an end portion of the side plate; and the narrow portionis formed on the intermediate plate.

There may be provided such a configuration that lower frame sideportions and the lower frame center portion are provided as a lowerframe, and the lower frame side portions include the narrow portions. Onthe lower frame side portion including the side plate and theintermediate plate, the horizontal portion formed on the lower frameside portion can be made thin to more easily be bent by forming theintermediate plates in the longitudinal direction of the lower frame,and by forming the narrow potions by machining the intermediate platesto form a part of each of the intermediate plates into a recessed shape.Further, this configuration can simplify the configuration of the lowerframe side portions. Moreover, each of the lower frame side portions isconstructed by the side plate and the intermediate plate, namely platemembers, and the weight can be extremely reduced compared to a casewhere the lower frame side portion is formed into a box shape or thelike.

Moreover, in this embodiment, preferably, a harness attachment portionbulging toward a side opposite to a bulging direction of the narrowportion is formed below the bent portion.

In this way, the rigidity of the lower frame against the load can beincreased by forming the harness attachment portions around the narrowportions, thereby forming multiple concavo-convex portions including thenarrow portions. Then, the load applied to the inclined portion and thebent portion can be received by the harness attachment portion byproviding the harness attachment portion below the bent portion of thenarrow portion, resulting in an increased rigidity of portions otherthan the narrow portions in the lower frame.

Moreover, the necessity of independently forming a member for attachinga harness is eliminated by providing the multiple concavo-convexportions and attaching the harness to the part thereof, resulting inspace saving. Further, the necessity of independent assembly of a memberfor attaching the harness is eliminated, resulting in a reducedmanufacturing process.

Further, preferably, the narrow portion is formed above the lower framecenter portion.

Preferably, the narrow portions formed on the lower frame side portionsare arranged at positions which do not overlap the lower frame centerportion (in more detail, above the lower frame center portion). If thenarrow portions are arranged at positions which do not overlap the lowerframe center portion, the rearward load applied to the seatback framedeforms the narrow portions more than the lower frame center portion.Thus, the impact energy is efficiently transmitted to the narrowportions. As a result, when a load in the rearward direction is appliedto the seatback frame by rear end collision or the like, deformation ofthe narrow portions is not prevented by the lower frame center portion,resulting in efficient absorption of the impact energy.

In an embodiment, preferably, a reinforcement portion that reinforcesthe lower frame is provided at a position displaced from the narrowportion in an up and down direction.

If the vehicle seat includes the reinforcement portion that reinforcesthe lower frame at a position displaced from the narrow portions in theup and down direction as described above, portions other than the narrowportions of the lower frame are reinforced by the reinforcement portion.Thus, when an impact load is applied, the seatback frame can berestrained from deforming starting from portions other than the narrowportions, and position restriction on the deformation portions andguidance of deformation can be facilitated on the seatback frame.

Moreover, preferably, the reinforcement portion is provided below thenarrow portion.

If the reinforcement portions are provided below the narrow portions,rigidity of the portions below the narrow portions are increased in thelower frame, and deformations below the narrow portions are restrainedwhen a rearward impact load is applied, resulting in efficienttransmission of the impact energy to the narrow portions. As a result,the position restriction on the deformation portions and the guidance ofdeformation are further facilitated on the seatback frame.

Further, preferably, the reinforcement portion is provided at a positionoverlapping at least partially the narrow portion in a front to backdirection.

As described above, if the reinforcement portion is provided at aposition overlapping at least partially the narrow portion in the frontto back direction, the deformations of the narrow portions by an impactload are not prevented, and the directions of the deformations of thenarrow portions can be regulated for an input load in a complexdirection. This configuration can further facilitate the guidance ofdeformation, can efficiently absorb the impact energy, and can properlydeform the seatback frame.

In an embodiment, preferably the vehicle seat further includes apressure receiving member that is connected to the pair of side framesvia a connection member to support an occupant; and an impact reducingmember that is arranged at least on one of the side frames and isconnected to the connection member, to move the pressure receivingmember rearward by a predetermined impact load applied to the pressurereceiving member.

As described above, rearward inclination (rearward movement) of anoccupant can be facilitated by receiving the body of the occupant movingrearward on the pressure receiving member upon rear end collision or thelike, and configuring the pressure receiving member to be able to moverearward. Then, the impact energy can be more efficiently transmitted tothe lower frame side portions constructing the seatback frame byfacilitating the rearward inclination of the occupant. As a result, theimpact energy due to a rear end collision or the like can be moreefficiently absorbed.

Accordingly, in an embodiment, there can be provided a vehicle seatwhich includes the narrow portions each provided with the horizontalportion and the inclined portion, in which only the horizontal portionsare bent, thereby efficiently absorbing an impact energy when an impactload is applied by a rear end collision or the like.

Accordingly, in an embodiment, the narrow portions formed on the lowerframe side portions can be bent by a large amount, and the impact energycan be more efficiently absorbed by the narrow portions.

Accordingly, in an embodiment, the number of components can be reduced,and a vehicle seat high in absorption efficiency of the impact energy byincreasing the rigidity of portions other than the narrow portions canbe provided.

Accordingly, in an embodiment, a vehicle seat which can more efficientlyabsorb impact energy without degradation of absorption efficiency of theimpact energy by way of the lower frame center portion upon rear endcollision can be provided.

Accordingly, in an embodiment, when an impact load is applied, theseatback frame can be prevented from deforming starting from portionsother than the narrow portions, and the position restriction of thedeformation portions, and the guidance of deformation can be facilitatedon the seatback frame.

Accordingly, in an embodiment, the deformations are restrained below thenarrow portions, and the position restriction of the deformationportions, and the guidance of deformation can be further facilitated.

Accordingly, in an embodiment, deformations of the narrow portions by animpact load are not prevented, and the direction of the deformations ofthe narrow portions can be regulated for an input load in a complexdirection.

Accordingly, in an embodiment, the vehicle seat does not prevent therearward inclination of the occupant, secures a sufficient sinkingamount, and efficiently absorbs the impact energy caused by the rearwardinclination load.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a seat according to a firstembodiment of the present invention.

FIG. 2 is a schematic perspective view of a seat frame according to thefirst embodiment of the present invention.

FIG. 3 is a front view of the seat frame according to the firstembodiment of the present invention.

FIG. 4 is a rear view of the seat frame according to the firstembodiment of the present invention.

FIG. 5 is a schematic perspective view of lower frame side portionsaccording to the first embodiment of the present invention.

FIG. 6 is a cross sectional view taken along the A-A line in FIG. 5.

FIG. 7 is an explanatory diagram showing a state of the lower frame sideportion after a rear end collision according to the first embodiment ofthe present invention.

FIG. 8 is a schematic perspective view of the seat according to a secondembodiment of the present invention.

FIG. 9 is a partially enlarged explanatory diagram of a lower framecenter portion and a frame side portion according to the secondembodiment of the present invention.

FIG. 10 is a partial cross sectional view of a lower frame according tothe second embodiment of the present invention.

FIG. 11 is a rear view of the seat frame according to the secondembodiment of the present invention.

DETAILED DESCRIPTION

A description will now be given of an embodiment of the presentinvention referring to drawings. It should be noted that members,arrangements, and the like described below do not limit the presentinvention, and can be modified in various ways within the purport of thepresent invention. Moreover, a vehicle herein refers to a vehicle fortravel on which a seat can be installed such as a ground travelingvehicle having wheels such as a motor vehicle and a railroad vehicle,and air planes and ships which do not travel on the ground. Moreover, anormal seating load includes a seating impact generated during seating,and a load during acceleration generated when the vehicle startsrapidly. Moreover, impact energy upon rear end collision is energy by alarge load generated upon rear end collision, is caused by a largecollision of a vehicle from behind or a serious collision during arearward travel, and does not include energy by a load in a load rangesimilar to a load generated during normal seating.

FIGS. 1 to 7 relate to a first embodiment of the present invention. Adescription will now be given of a vehicle seat S according to a firstembodiment referring to FIGS. 1 to 7.

The vehicle seat S is constructed by a seatback S1 (back portion), seatbase portion S2, and a headrest S3 as shown in FIG. 1, the seatback S1(back portion) and the seat base portion S2 are respectively formed byplacing cushion pads 1 a and 2 a on the seat frame F, and covering themwith skin materials 1 b and 2 b. The headrest S3 is formed by placing apad material 3 a on a core material (not shown) for a head portion, andcovering them with a skin material 3 b. Moreover, reference numeral 19denotes headrest pillars for supporting the headrest S3.

The seat frame F for the vehicle seat S is constructed by a seatbackframe 1 for constructing the seatback S1, and a seat base frame 2 forconstructing the seat base portion S2 as shown in FIG. 2.

The seat base frame 2 is formed by placing the cushion pad 2 a, andcovering the cushion pad 2 a with the skin material 2 b as describedabove, and is configured to support an occupant from the underside. Theseat base frame 2 is supported by a leg portion (not shown), innerrails, which are not shown, are attached to the leg portion, and areassembled to outer rails installed on a floor of a vehicle body to slidefor adjusting the position in a front to back direction.

Moreover, a back end portion of the seat base frame 2 is connected tothe seatback frame 1 via a reclining mechanism 11.

The reclining mechanism 11 includes at least a reclining shaft 11 aalong a rotation axis of the reclining mechanism 11, and the recliningshaft 11 a is arranged thorough shaft insertion holes 17 c (refer toFIG. 6) formed on the pair of lower frame side portions 17 (membersides) provided below the seatback frame 1 (in more detail, a pair ofside frames 15) to protrude therefrom on side portions of the seat frameF.

The seatback S1 is formed by placing the cushion pad 1 a on the seatbackframe 1, and covering the cushion pad 1 a with the skin material 1 b,and supports the back of the occupant from behind. According to thisembodiment, the seatback frame 1 is a frame body in approximately arectangular shape as shown in FIG. 2, and includes the side frames 15,an upper frame 16, and the lower frame side portions 17.

The two (the pair of) side frames 15 define a seatback width, and arearranged to be separated in the right and left direction, and to extendin the up and down direction. Then, the upper frame 16 for connectingthe upper end portion sides of the pair of the side frames 15 to eachother extends upward from the side frames 15. The upper frame 16 extendsupward from one of the side frames 15, bends, and extends to the otherside frame 15.

A lower frame of the seatback frame 1 is constructed by the lower frameside portions 17 and a lower frame center portion 18. The lower framecenter portion 18 (member center) is formed to connect the pair of thelower frame side portions 17 arranged to be separated in the right andleft direction to each other, and is arranged to be in contact with thelower frame side portions 17. The lower frame side portions 17 areconnected to bottom sides of the side plates 15 a of the side frames 15.Then, the lower frame side portions 17 are formed to extend below theside plates 15 a, and extend within a range which does not cause aproblem with the seat base frame 2.

Although, in the seatback frame 1 according to this embodiment, the sideframes 15 and the lower frame side portions 17 are formed by independentmembers, the side frames 15 and the lower frame side portions 17 may bean integral plate frame or the like.

Lower Frame Side Portion 17

The side frames 15, the lower frame side portions 17, and the lowerframe center portion 18 are formed as independent members, and can beeasily assembled.

The lower frame side portion 17 includes a side plate 17 a joined to theside plate 15 a of the side frame 15, and an intermediate plate 17 bformed to be folded from a rear end portion of the side plate 17 a atapproximately the right angle as shown in FIG. 5. The shaft insertionhole 17 c for inserting the reclining shaft 11 a is formed at a bottomof the side plate 17 a.

Moreover, multiple attachment holes 17 d for attaching the lower frameside portion 17 to the side frame 15 are formed above the shaftinsertion hole 17 c on the side plate 17 a. Holes are formed in lowerportions of the side frames 15 at positions corresponding to theattachment holes 17 d when the side plates 17 a overlap, and joiningelements such as bolts run through the holes formed on the side frames15 and the attachment holes 17 d of the lower frame side portions 17,thereby joining the side frames 15 and the lower frame side portions 17to each other.

Then, a flexible narrow portion 17 e as a weak portion for efficientlyabsorbing impact energy upon rear end collision is formed on each of theintermediate plate 17 b as shown in FIG. 6. The narrow portion 17 eserving as the weak portion is a recessed portion formed to beapproximately semicircular in cross section to bulge forward, and isformed inside the side frame 15 in the right and left direction, namelyalong the widthwise direction of the seat. In this way, a horizontalportion (horizontal potion 17 f) in the narrow portion 17 e formed to beapproximately semicircular in cross section on the lower frame sideportion 17 can bend, and deforms to collapse in the up and downdirection (refer to FIG. 7) when a predetermined impact load (impactload larger than that during normal seating) is applied to the seatbackframe 1 upon rear end collision or the like. As a result, the rearwardinclination load can be efficiently absorbed. Moreover, the horizontalportion 17 f is provided to extend along the seat width direction,namely the longitudinal direction of the lower frame center portion 18,and even when a load in the right and left direction is applied, a ridgeportion can receive the load, resulting in an extreme increase inrigidity of the lower frame side portion 17.

The horizontal portion 17 f extends to a border portion between theintermediate plate 17 b and the side plate 17 a as shown in FIG. 5, andthus tends to deform when a load is applied, thereby efficientlyabsorbing the energy of the rearward inclination load.

Then, the narrow portion 17 e bends upward as the narrow portion 17 eapproaches the inside of the seat, and extends to an upper end portionof the intermediate plate 17 b. In other words, the narrow portion 17 eincludes the horizontal portion 17 f and an inclined portion 17 hprovided to extend from the horizontal portion 17 f via a bent portion17 g.

As described above, the narrow portion 17 e is not configured to haveonly the horizontal portion 17 f extending straight in the horizontaldirection, but to include the bent portion 17 g, and the portion(inclined portion 17 h) which is provided to extend in a direction otherthan the approximately horizontal direction, namely an obliquedirection, can thus absorb energy when a load which deforms the seatbackframe 1 to incline the seatback frame 1 rearward is applied by the rearend collision or the like, for example, and increases in rigidityagainst the load.

Although the inclined portion 17 h may be formed to be approximatelyvertical with respect to the horizontal portion 17 f, the inclinedportion 17 h is preferably formed to be inclined with respect to thehorizontal portion 17 f. In other words, the inclined portion 17 h ispreferably configured to form an acute angle or an obtuse angle withrespect to the horizontal portion 17 f. If the inclined portion 17 h isformed to be approximately vertical with respect to the horizontalportion 17 f, the inclined portion 17 h increases the rigidity of theintermediate plate 17 b when a load to incline the seatback frame 1rearward is applied, and the horizontal portion 17 f is harder to bedeformed by the rearward inclination load. The inclined portion 17 h isconfigured to form an acute angle or an obtuse angle with respect to thehorizontal portion 17 f, the intermediate plate 17 b appropriatelydeforms, thereby bending the horizontal portion 17 f.

Moreover, a harness attachment portion 17 i bulging toward a sideopposite to the bulging direction of the narrow portion 17 e is formedbelow the bent portion 17 g. In other words, the harness attachmentportion 17 i is formed to bulge rearward below the bent portion 17 g. Inthis way, the multiple concavo-convex shapes are formed on theintermediate plates 17 b by forming the harness attachment portions 17 ion the side opposite to the bending direction of the bent portions 17 gof the narrow portions 17 e (namely, on an obtuse angle side formedbetween the horizontal portion 17 f and the inclined portion 17 h) onthe intermediate plates 17 b, resulting in an increase in rigidity ofthe lower frame side portions 17 (particularly rigidity in aneighborhood of the bent portions 17 g) against the load. As a result,when an impact load is applied upon rear end collision or the like, thehorizontal portion 17 f, the bent portion 17 g, and the inclined portion17 h of each narrow portion 17 e deform without bending portions otherthan the narrow portions 17 e to absorb impact energy.

As described above, the harness attachment portion 17 i is formed tobulge rearward at the position below the narrow portion 17 e on each ofthe intermediate plates 17 b, and functions as a reinforcement portionwhich prevents portions other than the narrow portion 17 e from bendingwhen an impact load is applied upon rear end collision. The increasedrigidity resulting from the concavo-convex shapes restricts the rearwarddeformations of the harness attachment portions 17 i, the seatback frame1 can be prevented from deforming from portions other than the narrowportions 17 e, and the position restriction on the deformation portionsand the guidance of deformation are facilitated on the seatback frame 1.

Multiple attachment holes 17 j are also formed on the intermediate plate17 b. Joining elements such as bolts pass through the attachment holes17 j when other member (such as an actuator) is attached to the seatframe F.

There are provided such effects that a space is saved for attachingother member and the number of components is further reduced byproviding the harness attachment portion 17 i and the attachment holes17 j on the intermediate plate 17 b in this way. Moreover, the harnessattachment portion 17 i has the function as the reinforcement portionprovided rearward of each of the narrow portions 17 e, can provide boththe function of attaching components and the function as the deformationguide for restricting the deformation portions of the seatback frame,and contributes to the deformations of the seatback frame while reducingthe number of components.

The lower frame center portion 18 is joined to the side plates 17 a orthe intermediate plates 17 b of the pair of lower frame side portions17. If the lower frame center portion 18 is joined to both the sideplates 17 a and the intermediate plates 17 b, attachment rigidity isincreased. Further, if side end portions of the lower frame centerportion 18 are formed to come in contact with the side plates 17 a,rigidity against a lateral load is increased. Although the lower framecenter portion 18 is arranged forward of the intermediate plates 17 b inthis embodiment, the lower frame center portion 18 may be arrangedbehind the intermediate plates 17 b.

The narrow portions 17 e are preferably formed at positions which do notoverlap the lower frame center portion 18, and are above the lower framecenter portion 18. If there is provided such a configuration that thenarrow portions 17 e are provided at positions which do not overlap thelower frame center portion 18 as described above, when a load in thedirection of rearward inclination is applied to the seatback frame 1,the deformations of the narrow portions 17 e are not prevented by thelower frame center portion 18.

In other words, the lower frame center portion 18 is at a positiondisplaced in the up and down direction from the narrow portions 17 e,and is provided below the narrow portions 17 e. As a result of thisarrangement, the lower frame center portion 18 functions as areinforcement portion for increasing rigidity of portions below thenarrow portions 17 e when a load in the direction of rearwardinclination is applied to the seatback frame 1 upon rear end collision.Thus, the lower frame side portions 17 can be prevented from bendingfrom portions other than the narrow portions 17 e, and the positionrestriction on the deformation portions of the seatback frame 1 and theguidance of deformation are facilitated.

The upper frame 16 formed by a member having a closed sectional shape(such as a circular or rectangular sectional shape) is bent in asubstantially U shape as shown in FIG. 2. Then, the side surfaceportions 16 a of the upper frame 16 are arranged to partially overlapthe side plates 15 a of the side frames 15 in the up and down direction,and are anchored to the side frames 15 at the overlapped portions.Although the upper frame 16 is constructed by the tubular member havingthe circular cross section in the first embodiment, the upper frame 16may be constructed by a tubular member having a rectangular crosssection.

Moreover, the headrest S3 is arranged above the upper frame 16. Theheadrest S3 is constructed by providing the pad member 3 a on an outerperipheral portion of the core material (not shown), and covering thepad material 3 a with the skin material 3 b as described before. Pillarsupport portions 19 a are arranged on the upper frame 16. Headrestpillars 19 (refer to FIG. 1) for supporting the headrest S3 are attachedvia guide locks (not shown) to the pillar support portions 19 a toattach the headrest S3. Although an example where the seatback S1 andthe headrest S3 are formed independently of each other is described inthe first embodiment, the seatback S1 and the headrest S3 may beintegrated, which is a configuration of the bucket type seat.

The side frames 15 partially constructing the seatback frame 1 areextending members for constructing side surfaces of the seatback frame 1as shown in FIG. 2, and include the side plates 15 a in a flat plateshape, front edge portions 15 b each bent inward and folded back in a Ushape from a front edge portion (end portion located on the vehiclefront side) of the side plates 15 a, and rear edge portions 15 c eachbent inward in an L shape from rear end portions.

A protruded portion 15 d protruding toward the rear edge portion 15 cside is formed on the front edge portion 15 b according to thisembodiment, and a lock hole serving as a lock portion for locking anextension coil spring 35 is formed on the protruded portion 15 d.

Then, moving members 30, described later, are locked to the side frames15 according to this embodiment. A configuration and an action of themoving members 30 are described later.

Pressure Receiving Member 20

The pressure receiving member 20 as a pressure receiving member forsupporting the cushion pad 1 a from behind is arranged on an inside areaof the seatback frame 1 inside the seatback frame 1 (between the sideframes 15).

The pressure receiving member 20 according to this embodiment is amember obtained by forming a resin into a plate in approximately arectangular shape, and smooth concavo-convex portions are formed on asurface in contact with the cushion pad 1 a. Pawl portions for locking awire 21 serving as a top connection member, and a wire 22 serving as abottom connection member are formed on a top side and a bottom side ofthe pressure receiving member 20 as shown in FIG. 2.

The pressure receiving member 20 according to this embodiment issupported by the connection members. In other words, the two wires 21and 22 serving as the connection members are provided between the sideframes 15 on the both sides, and engage with the pressure receivingmember 20 by the pawl portions formed at predetermined positions on thetop side and the bottom side on the rear side of the pressure receivingmember 20 to support the pressure receiving member 20 on a rear surfaceof the cushion pad 1 a. The wires 21 and 22 are formed by a springysteel wire material, and have concavo-convex portions, which are bentportions, formed thereon.

Particularly, the wire 21 positioned above in the two wires 21 and 22locked to the pressure receiving member 20 according to this embodimentis constructed by a wire thinner than the wire 22 positioned below. As aresult, the pressure receiving member 20 tends to move rearward more atthe upper portion than at the lower portion.

Moreover, the wire 22 is constructed by a thicker wire material, is thushigh in rigidity, and is hard to deform during normal seating. Thus, theupper portion of the pressure receiving member 20 supported by the wire21 constructed by the thinner wire material tends to move rearward, andthe lower portion of the pressure receiving member 20 supported by thewire 22 constructed by the thicker wire material does not move rearwardgreatly during normal seating. As a result, the upper portion of thepressure receiving member 20 properly sinks rearward, and the lowerportion supports the body of the occupant during normal seating, therebypreventing sense of seating from degrading.

Further, there is provided such a configuration that the wires 21 and 22have the concavo and convex portions formed thereon, and are thusdeformed greatly by a load more than a predetermined load (load largerthan a load for moving or pivoting impact reducing members describedlater) to move rearward the pressure receiving member 20 by a largermovement quantity.

As illustrated in FIG. 2, both end portions of the wire 21 locked to thetop side out of the two wires 21 and 22 locked to the pressure receivingmember 20 according to this embodiment are hooked on journal portions 21a provided on the side frames 15 on the both sides. Both end portions ofthe wire 22 locked to the bottom side are hooked on the moving members30 installed on the right and left side frames 15.

The wire 22 constructed by the thicker wire material than the wire 21 ishard to deform as described above, and the lower portion of the pressurereception portion 20 is thus hard to move rearward during normalseating. Thus, the moving members 30 are attached to the end portions ofthe wire 22 for securing a sufficient sinking amount upon rear endcollision.

Moving Member 30

The moving members 30 serving as impact reducing members are movedrearward of the vehicle by an impact load transmitted via the connectionmember (wire 22), and simultaneously move rearward the pressurereceiving member 20 to move rearward the occupant when an impact loadlarger than the predetermined impact load is applied to the pressurereceiving member 20 upon rear end collision or the like. The “movement”refers to motions such as horizontal translation or pivoting. Adescription will now be given of the moving members 30 that pivot aboutshaft portions 32 as pivot axes according to this embodiment. Thepressure receiving member 20 can be moved greatly rearward of thevehicle by the movement of the moving members 30 to consequently moverearward the occupant, and the load applied to the occupant can beefficiently reduced.

The moving members 30 are pivotally journaled via the shaft portions 32serving as pivot axes to the insides of the side plates 15 a of the sideframes 15 on the both sides, lock the wire 22 at the bottom positionserving as the connection member, and are connected to the springs(extension coil springs 35) serving as biasing elements for biasing thewire 22 according to this embodiment as shown in FIG. 2. In other words,the moving members 30 are connected to the biasing elements 35, and areconfigured to bias the pressure receiving member 20 via the wire 22serving as the connection member forward of the seatback frame 1.

Then, the moving members 30 according to this embodiment are journaledby the pivotable shaft portions 32 to the inside of the side frames 15,in more detail, to convex portions 15 e formed by bulging parts of theside plates 15 a toward the inside of the seat.

The above-described moving members 30 are attached to the side frames 15on both sides, both ends of the wire 22 are hooked to the moving members30 respectively arranged on both sides, and there is provided such aconfiguration that the respective moving members 30 are individuallyactivated.

According to this embodiment, the moving members 30 are attached to theside frames 15 on both sides, and the moving members 30 attached to bothsides are configured to move (pivot) independently of each other. As aresult, if a generated load is biased in the right and left direction,the moving members 30 attached to the side frames 15 on both sides move(pivot) independently of each other according to the load, and the bodyof the occupant can sink according to the magnitude of the impact load.

A description will now be given of configurations and actions of thepressure receiving member 20 and the moving members 30.

A tensile force of moving rearward (pivoting) the moving members 30 viathe cushion pad 1 a, the pressure receiving member 20, and the wire 22inside the seatback S1 is generated during normal seating where theoccupant is seated. The extension coil springs 35 bias the movingmembers 30 to move (pivot) forward of the seatback frame 1. On thisoccasion, the extension coil springs 35 connected to the moving members30 have a load characteristic which does not present an extension in aload range generated during normal seating, and the moving members 30are always held at initial positions. In other words, there is providedsuch a configuration that a force of returning the moving members 30 tothe initial state resisting the force of moving (pivoting) the movingmembers 30 is maximized during normal seating.

Then, a movement preventing portion 39 provided for each of the movingmembers 30 is an abutment portion for abutting against a rear edgeportion 15 c of the side frame 15 to prevent the motion (pivoting) afterthe moving member 30 moves (pivots).

The movement preventing portion 39 of the moving member 30 is integrallyformed by extending the moving member 30 in an outer peripheraldirection, an abutment surface thereof abuts against the side frame 15(rear edge portion 15 c in more detail) after the movement (pivot), andthe movement (pivot) of the moving member 30 can be stably and reliablystopped even if an impact load more than the predetermined load isapplied to the pressure receiving member 20 due to a rear end collisionor the like.

The movement preventing portion 39 is formed at a position which doesnot interfere with the biasing element (extension coil spring 35) andthe connection member (wire 22).

Although the movement preventing portions 39 of the moving members 30directly abut against the side frames 15 to prevent the movement(pivoting) according to this embodiment, a sound reducing member such asrubber having such a thickness as not to obstruct stability of stoppingthe movement (pivoting) of the moving members 30 may be attached to eachof gaps between the movement preventing portion 39 and the side frame 15in order to remove noise generated upon the abutment, this configurationcan stably prevent the movement (pivoting), and a sound reduction effectis expected.

The moving members 30 abut against the side frames 15 (portions formedby partially cutting out the convex portions 15 e in more detail) in anormal state, which prevents a force applied upward by the extensioncoil springs 35, and restricts a movement (pivoting) range to prevent anexcessive forward movement (pivoting) of the moving members 30.

Then, when the occupant starts moving rearward by inertia upon rear endcollision, a load thereof generates a tension in the direction to move(pivot) rearward the moving members 30 via the pressure receiving member20 and the wire 22 locked to the pressure receiving member 20. Thetensile force extends the extension coil springs 35, which hold themoving members 30 at the initial positions on this occasion, to form aload sufficient to move (pivot) rearward the moving members 30.

A threshold for a force starting the movement (pivoting) of the movingmembers 30 is set to a value larger than the normal seating load.

In this situation, regarding the threshold for the force starting themovement (pivoting) of the moving members 30, the load applied to theseatback S1 is approximately 150 N in the normal seating state (here,small impacts generated by a seating impact and a rapid start of thevehicle are excluded), and the threshold is thus preferably a valuelarger than 150 N.

Moreover, considering the seating impact generated during normalseating, and the load caused by an acceleration generated by the rapidstart of the vehicle or the like, the threshold is preferably set to avalue larger than 250 N, if the threshold is set in this way, the movingmembers 30 are not activated in cases other than the rear end collision,and the stable state can be maintained.

The wire 22 hooked on the moving members 30 can be moved rearward bymoving (pivoting) the moving members 30 rearward as described above, andsimultaneously, the pressure receiving member 20 locked to the wire 22and the cushion pad 1 a supported by the pressure receiving member 20can be moved rearward to sink the occupant into the seatback S1.

The moving members 30 have the movement (pivoting) characteristic forthe tensile force generated via the wire 22 as described above, and canthus reliably and efficiently sink the occupant into the cushion pad 1 aof the seatback S1 when a rear end collision is generated.

The back of the occupant sinks into the seatback S1 and thus movesrearward on this occasion, the position of the headrest S3 does notchange with respect to the seatback S1, a gap between the headrest S3and the head of the occupant decreases, the head can thus be supportedby the headrest S3, and an impact applied to the neck can be efficientlyreduced.

Although the example where the moving members 30 are provided on theside frames 15 on both right and left sides is described in theembodiment, there may be provided such a configuration that the movingmember 30 may be provided only on one of the side frames 15. In thiscase, there may be provided such a configuration that the wires 21 and22 are directly locked to the side frame 15 on which the moving member30 is not provided.

As described above, in the vehicle seat S, the moving members 30 servingas the impact reducing members are arranged on the side frames 15 torearward sink the body of occupant upon rear end collision. Then, thenarrow portions 17 e are provided on the lower frame side portions 17 toefficiently absorb energy of the rearward inclination load applied tothe seatback frame 1 by the body of the occupant sinking rearward.

The narrow portion 17 e including the horizontal portion 17 f and theinclined portion 17 h is formed on each of the lower frame side portions17 as described above. The narrow portions 17 e are formed to bulgetoward the seating side of the occupant, and each of the lower frameside portions 17 deforms to bend about the narrow portion 17 e as a basepoint, thereby absorbing impact energy upon rear end collision or thelike when the occupant rapidly moves rearward upon rear end collision.The protrusion may bulge rearward if the lower frame side portion 17 canbe sufficiently bent.

The lower frame side portion 17 includes the narrow portion 17 e havingthe cross section in approximately the arc shape on the intermediateplate 17 b forming the lower frame side portion 17 as shown in FIG. 6.Then, there is provided such configuration that, when the occupant movesrearward, and a load of rearward inclination is applied to the seatbackframe 1 upon rear end collision or the like, the narrow portions 17 edeform as shown in FIG. 7, and the intermediate plates 17 b bendrearward about the narrow portions 17 e as the base points.

Thus, the plate thickness of portions constructing the narrow portions17 e may be formed to be thin in order to facilitate the deformations ofthe narrow portions 17 e as long as the narrow portions 17 e havestrength withstanding the normal load.

Then, the narrow portion 17 e is constructed by the horizontal portion17 f and the inclined portion 17 h across the bent portion 17 g as aborder.

In this way, the inclined portion 17 h is provided in addition to thehorizontal portion 17 f, which enables not only the absorption of theload energy by deformation of the horizontal portion 17 f, but also theincrease in strength against the load by the inclined portion 17 h.Thus, portions other than the horizontal portion 17 f are prevented fromdeforming, and the rigidity of the lower frame side portion 17 can beincreased, resulting in efficient absorption of the impact energy uponrear end collision.

Further, the vehicle seat S includes the pressure receiving member 20connected to the moving members 30, and can thus sufficiently sink theoccupant in the seatback S1 upon rear end collision or the like. Then,the narrow portions 17 e of the lower frame (lower frame side portions17 in more detail) include the inclined portions 17 h, and theintermediate plates 17 b thus have proper rigidity. The sinking of thepressure receiving member 20 and the moving members 30 with respect tothe side frames 15 and the upper frame 16 can thus be facilitated,resulting in efficient absorption of the impact energy generated by arear end collision or the like.

A description will now be given of the vehicle seat according to asecond embodiment referring to FIGS. 8 to 11. In the second embodiment,like members, arrangements, and the like are denoted by the samenumerals as of the first embodiment, and a detailed description thereofis therefore omitted.

A lower frame center portion 58 of the vehicle seat S according to thisembodiment is formed by folding a single plate body into approximately ahollow quadrangular prism form, and includes a forward bulging portion58 a, a rear surface 58 b opposed to the forward bulging portion 58 a,and a connection surface 58 c for connecting the forward bulging portion58 a and the rear surface 58 b to each other as shown in FIGS. 8 to 10.Regarding the lower frame center portion 58 according to thisembodiment, the forward bulging portion 58 a is arranged to bulgeforward of the reclining shaft 11 a, thereby covering the recliningshaft 11 a from the front side.

The lower frame center portion 58 according to this embodiment isconnected to the lower frame side portions 17 by joining the rearsurface 58 b opposed to the forward bulging portion 58 a and arranged onthe rear side to the intermediate plates 17 b of the lower frame sideportions 17. The rear surface 58 b and the lower frame side portions 17may be joined by way of any method such as welding or fastening byfasteners such as screws and bolts.

The lower frame center portion 58 is arranged at a positioncorresponding to the lower back of the occupant when the occupant isseated, and is arranged forward of the narrow portions 17 e as shown inFIG. 10. Thus, the lower frame center portion 58 receives an impact loadapplied by the back of the occupant via the cushion pad 1 a and the skinmaterial 1 b placed on the seatback frame 1 upon rear end collision on apart forward of the intermediate plates 17 b of the lower frame sideportions 17, and functions as a reinforcement portion for increasing therigidity of the lower frame side portions 17 against the impact load.

If the reinforcement portion is arranged forward of the narrow portions17 e, an input of the load from the front side to portions of theseatback frame 1 overlapping the reinforcement portion in the front toback direction is restricted, and deformations are restrained fromgenerating from portions other than the narrow portions 17. Thus, whenan impact load is applied from the front side, the seatback frame 1 canbe prevented from deforming starting from portions other than the narrowportions 17 e, and the position restriction on the deformation portions,and the guidance of deformation can be facilitated on the seatback frame1.

The lower frame center portion 58 serving as the reinforcement portionis at a position displaced from the narrow portions 17 e in the up anddown direction, and is below the narrow portions 17 e, and a upper end58 d of the lower frame center portion 58 overlaps the narrow portions17 e in the front to back direction as shown in FIGS. 9 and 10. Further,the rear surface 58 b, which is a joint surface to the intermediateplates 17 b is attached to the position which does not overlap thenarrow portions 17 e in the front to back direction, and is below thenarrow portions 17 e. Moreover, an upper end 58 e of the rear surface 58b is arranged below the horizontal portions 17 f to align with theextension direction of the horizontal portions 17 f of the narrowportions 17 e, namely the longitudinal direction (seat width direction)of the lower frame center portion 58.

In this way, the lower frame center portion 58 is arranged at theposition displaced in the up and down direction from the narrow portions17 e, namely at a different level, and the deformations of the narrowportions 17 e generated when an impact load is applied to the rear sideof the seatback frame 1 are not prevented by the lower frame centerportion 58. Moreover, the seatback frame 1 can be restrained fromdeforming from portions other than the narrow portions 17 e, and theposition restriction on the portions where the seatback frame 1 deformsand the guidance of deformation are facilitated. According to thisembodiment, the lower frame center portion 58 is arranged below thenarrow portions 17 e, more specifically, the rear surface 58 b of thelower frame center portion 58 is attached to the intermediate plates 17b below the narrow portions 17 e, rigidity below the narrow portions 17e thus increases to restrain deformations, and the impact energy uponrear end collision can be efficiently transmitted to the narrow portions17 e.

Moreover, at least a part of the lower frame center portion 58, theupper end 58 d according to this embodiment, is arranged at the positionoverlapping the narrow portions 17 e in the front to back direction, theinput direction can thus be regulated for an input load in a complexdirection, the direction of the deformations of the narrow portions 17 ecan be regulated, and the portions generating the deformations of theseatback frame 1 can be more properly restricted.

Further, the upper end 58 e of the rear surface 58 b is aligned with theextension direction of the horizontal portions 17 f of the narrowportions 17 e, and the guidance of the direction of the deformations anda deformation shape of the seatback frame 1 can be facilitated.

Side end portions 58 f on both right and left sides of the forwardbulging portion 58 a according to this embodiment are separated from theside plates 17 a of the lower frame side portions 17, and are not fixedto the side portions of the seatback frame 1. Although FIG. 9 shows onlythe side end portion 58 f on the left side viewed from the front side ofthe vehicle seat S, the side end portion on the right side has the sameconfiguration. In this way, the configuration where the forward bulgingportion 58 a is not connected to the side plates 17 a does notexcessively increase the rigidity of reinforcement portion, and does notinfluence the deformations of the seatback frame 1 upon impact load.

Although the reinforcement portion is arranged below the narrow portions17 e which are the portions where the deformations (bends) of theseatback frame 1 are generated according to this embodiment, there maybe provided such a configuration that the reinforcement portion may beprovided above the portions where the deformations are generated as therelationship between the portions where the deformations are generatedand the reinforcement portion. If the reinforcement portion is arrangedat the position which is above and does not overlap, in the front toback direction, the portions where the deformations are generated inthis way, the position restriction on the portions where thedeformations are generated is facilitated similarly.

A description will now be given of actions of the forward bulgingportion 58 a and the moving members 30 upon rear end collision.

The forward bulging portion 58 a according to this embodiment isarranged at the position corresponding to the back of the occupant whenthe occupant is seated, and is configured to bulge toward the back ofthe occupant. As a result, the forward bulging portion 58 a has afunction of a back entrance preventing member for pushing and stopping arearward movement of the back of the occupant upon rear end collision.

When the occupant receives an impact upon rear end collision, theoccupant is rapidly moved rearward, and the lower back of the occupantcomes in contact with the forward bulging portion 58 a, and the rearwardmovement is stopped. As a result, the entire upper body of the occupantinclines (rotates) rearward, and an upper portion of the upper bodymoves rearward more, and sinks into the seatback S1. Then, the loadcaused by the rearward movement of the occupant is applied to thepressure receiving member 20, the tensile force is applied in thedirection of moving (pivoting) the moving members 30 rearward via thewire 22 locked to the pressure receiving member 20, and the movingmembers 30 move rearward. The movement of the moving members 30 greatlymoves the pressure receiving member 20 rearward, the sinking quantity ofthe occupant increases, and the impact load is absorbed.

The moving members 30 are provided above the positions of the narrowportions 17 e on the side frames 15, the impact load is applied abovethe narrow portions 17 e, and the impact load can be absorbed by thedeformations of the seatback frame 1.

The impact load can be absorbed by the action of the moving members 30,the impact load can be absorbed by the action of the narrow portions 17e as described above, and the impact load can thus be absorbed moreefficiently.

Although the lower frame center portion 58 is arranged as thereinforcement portion on the front side of the narrow portions 17 e inthe second embodiment, the arrangement of the reinforcement portion isnot limited to this example, and the reinforcement portion may bearranged on the rear side of the narrow portions 17 e.

FIG. 11 is a rear view of the seat frame showing another example of thereinforcement portion according to the second embodiment. Areinforcement member 59 in a plate shape is provided as thereinforcement portion rearward of the lower frame (lower frame sideportions 17 and the lower frame center portion 58) in this example asshown in FIG. 11. The reinforcement member 59 is provided at a positiondisplaced from the narrow portions 17 e in the up and down direction andbelow the narrow portions 17 e, and a upper end 59 a is aligned with theextension direction of the horizontal portions 17 f, namely, in thelongitudinal direction (seat width direction) of the lower frame centerportion 58.

If the reinforcement member 59 is arranged rearward of the narrowportions 17 e in this way, when an impact load is applied, a rearwarddeformation of a portion of the seatback frame 1 overlapping thereinforcement member 59 in the front to back direction is restricted,and deformations are restrained from generating from portions other thanthe narrow portions 17 e. As a result, the position restriction on thedeformation portions and the guidance of deformation are facilitated onthe seatback frame 1.

The vehicle seat according to the second embodiment can stably deformthe seatback frame at the specific portions for a complex input loadupon rear end collision, and can increase rigidity of portions otherthan the specific portions which tend to deform, thereby facilitatingthe position restriction on the deformation portions, and facilitatingthe guidance of deformation as described above. Thus, even if a complexinput load is applied upon rear end collision, impact energy can beefficiently and stably absorbed. Further, the back entrance preventingmember is provided for stopping the rearward movement of the lower backof the occupant upon rear end collision, the upper body of the occupantcan be greatly moved rearward, thereby increasing the sinking quantityof the occupant, and the impact load can be more efficiently absorbed.

Although the respective embodiments are described for the seatback ofthe front seat of a motor vehicle as specific examples, the seatback isnot limited to the example, and it should be understood that the sameconfiguration can be applied to the seatback of a rear seat.

TABLE OF REFERENCE CHARACTERS s vehicle seat s1 seatback s2 seat base s3headrest f seat frame 1 seatback frame 2 seat base frame 1a, 2a, 3acushion pad (pad material) 1b, 2b, 3b skin material 11 recliningmechanism 11a reclining shaft 15 side frame 15a side plate 15b frontedge portion 15c rear edge portion 15d protruded portion 15e convexportion 16 upper frame 16a side surface portion 17 lower frame sideportion (lower frame) 17a side plate 17b intermediate plate 17c shaftinsertion hole 17d, 17j attachment hole 17e narrow portion 17fhorizontal portion 17g bent portion 17h inclined portion 17i harnessattachment portion (reinforcement portion) 18 lower frame center portion(lower frame, reinforcement portion) 19 headrest pillar 19a pillarsupport portion 20 pressure receiving member 21 wire (connection member,upper connection member) 21a journal portion 22 wire (connection member,lower connection member) 30 moving member (impact reducing member) 32shaft portion 35 extension coil spring (biasing means) 39 movementpreventing portion 58 lower frame center portion (lower frame,reinforcement portion) 58a forward bulging portion 58b rear surface 58cconnection surface 58d, 58e upper end 58f side end portion 59reinforcement member 59a upper end

What is claimed is:
 1. A vehicle seat comprising: a pair of side framesthat are arranged on the side; and a lower frame that connect lowerportions of the pair of side frames to each other, wherein a narrowportion including: a horizontal portion formed inside the pair of sideframes along a longitudinal direction with a flexibility against a loadequal to or more than a predetermined impact load, and an inclinedportion extending from the horizontal portion via a bent portion insidethe pair of side frames is formed on the lower frame.
 2. The vehicleseat according to claim 1, wherein: the lower frame includes a pair oflower frame side portions arranged below the pair of side frames, and alower frame center portion that connects the pair of lower frame sideportions to each other; the lower frame side portion includes a sideplate joined to a side plate of the side frame, and an intermediateplate formed by being bent from an end portion of the side plate; andthe narrow portion is formed on the intermediate plate.
 3. The vehicleseat according to claim 1, wherein a harness attachment portion bulgingtoward a side opposite to a bulging direction of the narrow portion isformed below the bent portion.
 4. The vehicle seat according to claim 2,wherein the narrow portion is formed above the lower frame centerportion.
 5. The vehicle seat according to claim 1, wherein areinforcement portion that reinforces the lower frame is provided at aposition displaced from the narrow portion in an up and down direction.6. The vehicle seat according to claim 5, wherein the reinforcementportion is provided below the narrow portion.
 7. The vehicle seataccording to claim 5, wherein the reinforcement portion is provided at aposition overlapping at least partially the narrow portion in a front toback direction.
 8. The vehicle seat according to claim 1, furthercomprising: a pressure receiving member that is connected to the pair ofside frames via a connection member to support an occupant; and animpact reducing member that is arranged at least on one of the sideframes and is connected to the connection member, to move the pressurereceiving member rearward by a predetermined impact load applied to thepressure receiving member.